DEAR DR. BLONZ: There are a number of weight-loss teas at my drug store, and I was wondering which, if any, are worth consideration. -- S.C., San Jose, California

DEAR S.C.: As a basic concept, consuming liquids with (or before) a meal can help you feel fuller, and can therefore cut down the volume of food you eat. While many claim to have special metabolic powers, "weight-loss teas" usually rely on this most natural phenomenon to accomplish their goal.

Some such products might include herbal diuretics, such as couch grass, buchu, dandelion, uva-ursi and butcher's broom. The taking of a diuretic tea can decrease the total amount of water in the body, which will impact the numbers on the scale. But it is only water you are losing, not excess body fat. What's worse, it tends to be a short-term effect, with the water weight usually returning once the regimen is stopped.

Tea is a great beverage, and we are learning that some of the compounds found in green, black and oolong teas offer health benefits. That should be the motivator for drinking it -- not the promise of weight loss. Dramatic claims of success should be viewed with great skepticism.

One product I recall came in a package that displayed a slim woman on the front. The literature indicated that drinking the tea would facilitate the shedding of unwanted weight, but the product was nothing more than a plain black tea of modest quality. If you looked inside the package, there was a piece of paper that explained that you had to eat less and exercise more for the weight-loss plan to work. What a novel approach.

DEAR DR. BLONZ: Have you written about noncaloric sweeteners such as stevia and sucralose? Some of my friends are concerned about the safety of these sweeteners. -- S.S., Portland, Oregon

DEAR S.S.: Sugar substitutes provide few or no calories and have minimal effect on blood sugar, which is a plus for people with diabetes. Then there is the fact that they do not contribute to tooth decay. But while a sugar-substituted dessert, for example, succeeds in putting fewer calories on the plate, there is no reliable evidence that it works as a weight-loss strategy.

A paper by Richard Mattes in the 2009 American Journal of Clinical Nutrition reported that the addition of noncaloric sweeteners to diets posed no benefit for weight loss, or reduced weight gain, unless accompanied by energy (calorie) restriction.

I refrain from encouraging the consumption of noncaloric sweeteners -- not because they are necessarily dangerous, but because I don't encourage seeking out excessive sweetness. The Berkeley Wellness letter has a simple and straightforward piece on the various options: tinyurl.com/zxwf6zs.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I see articles on the benefits of "folate," but the nutrition and supplement facts panels only list "folic acid." Is folate the same as folic acid, or is it something different? -- T.T., Dallas, Texas

DEAR T.T.: Folic acid and folate are essentially the same active compound. Throughout its history, this vitamin has gone by many different names, including Wills factor, anti-anemia factor, PGA, vitamin M, vitamin Bc, factor R, SLR factor, vitamin U, factor U, vitamin B9, vitamin B10 and vitamin B11.

The different names can be explained by the fact that various laboratories were doing research on the same substance at the same time, and many were working on related compounds. There was a level of competition to discover essential compounds, and very little information sharing. Scientific prestige and naming rights were a side benefit to the individual or lab whose findings stood the test of time.

"Folate" is a generic term referring to a family of related compounds, the simplest of which is folic acid. You can think of the folates as folic acid with a side-chain component attached. In nature, it is active in metabolic reactions, and often referred to as folate. When spoken about as a nutrient, or when listed on a product label, it is called folic acid.

Whatever you want to call it, folic acid is a key compound in human nutrition. An inadequate intake of this nutrient is associated with a number of different ailments, including heart disease and certain birth defects. But you don't need megadoses to avoid these problems; one can get all the folate they need from a healthy diet. Good sources include leafy greens, organ meats, legumes, orange juice, beets, avocado and broccoli.

DEAR DR. BLONZ: Does pressure-cooking vegetables deplete their vitamins tremendously? -- E.R., San Jose, California

DEAR E.R.: All forms of cooking deplete nutrients to some degree. The actual nutrient losses during cooking depend on a number of factors, including temperature, cooking time, type of food, size of the food pieces and how much water is used (if any). With all these variables, the amount of loss will vary with the type of nutrient.

Cooking water, if discarded, will deplete some of the water-soluble vitamins. Heat, regardless of its source, can affect the fat-soluble vitamins, vitamin C and thiamin. The most stable of the nutrients are the minerals. Unless a large amount of water is used to cook a food that has a small particle size, and that water is then discarded, these nutrients will remain in the finished product.

Because cooking in a pressure-cooker typically uses less water and shortens cooking times, more of the nutrients will remain.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: At a recent lunchtime discussion, someone strongly stated the opinion that we should not mix proteins and carbohydrates at the same meal. They also said we should always eat fruit all by itself. I expressed general skepticism, but the person offering this was very intelligent; I was not certain exactly how to counter these arguments. -- A.M., Santa Clara, California

DEAR A.M.: This "don't mix food types" argument is not new. It is based on the dubious "theory" that it is not so much the foods themselves, but the way they are combined, that holds the key to health.

Such ideas appeared in a 1922 book titled "Mucusless Diet Healing System" by Arnold Ehret. There have been many reincarnations since, the classic one being the 1951 "Food Combining Made Easy" by Herbert Shelton, who started Dr. Shelton's Health School in San Antonio, Texas.

According to this notion, easy-to-digest foods such as fruits or other carbohydrates should never be eaten with proteins or fatty foods, which take longer to digest. To do so would delay the digestion of the carbohydrates, and in the case of fruit, allow the fruit sugar to ferment and putrefy as it waits its turn. The theory then imagines that this is responsible for today's health issues.

Other forbidden combinations include starchy foods, such as bread or potatoes, together with proteins, such as meat or fish. The theory stems, in part, from the fact that the body uses an acid (low pH) environment to digest protein, while it relies on an alkaline (higher pH) environment to digest carbohydrates.

There might be more interest in the theory if all the foods we ate were digested in the same location at the same time, but this is not the way it works. There are separate digestive enzymes for the proteins, carbohydrates and fats in our foods, and they operate in different regions of the digestive system. The treatments given to one type of food do not interfere with the others.

Protein, for example, is first denatured in the stomach by subjecting it to an acid environment. This, plus the churning by the stomach muscles, helps to break down the protein tissue so that the digestive enzymes will have an easier job. Once out of the stomach, the body neutralizes the acid; the rest of the digestive process, including the digestion and absorption of protein, carbohydrate and fat, takes place in a more alkali environment. If starches are present in a protein-based meal, they just hang out, waiting for their turn. The idea that they would ferment makes little sense -- especially in light of the fact that the acid environment of the stomach is not conducive to fermentation.

No doubt, many of us have found that certain foods or food combinations work best for us, and our bodies do seem to get used to the way we eat. But this is more a product of habit-bred efficiency than a requirement of the human species. There appears to be no physiological reason that we have to refrain from including a variety of foods at every meal.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.